We describe complex organic mixture analysis by 21 tesla (T) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Ultrahigh mass-resolving power (m/Δm 50% > 2 700 000 at m/z 400) ...and mass accuracy (80 ppb rms) enable resolution and confident identification of tens of thousands of unique elemental compositions. We demonstrate 2.2-fold higher mass-resolving power, 2.6-fold better mass measurement accuracy, and 1.3-fold more assigned molecular formulas compared to our custom-built, state-of-the-art 9.4 T FT-ICR mass spectrometer for petroleum and dissolved organic matter (DOM) analyses. Analysis of a heavy petroleum distillate exemplifies the need for ultrahigh-performance mass spectrometry (49 040 assigned molecular formulas for 21 T versus 29 012 for 9.4 T) and extends the identification of previously unresolved Oo, SsOo, and NOo classes. Mass selective ion accumulation (20 Thompson isolation) of an asphalt volcano sample yields 462 resolved mass spectral peaks at m/z 677 and reveals previously unresolved CcHhNnOoSs mass differences at high mass (m/z > 600). Similar performance gains are realized in the analysis of dissolved organic matter, where doubly charged Oo species are resolved from singly charged SOo species, which requires a mass-resolving power greater than 1 400 000 (at m/z 600). This direct comparison reveals the continued need for higher mass-resolving power and better mass accuracy for comprehensive molecular characterization of the most complex organic mixtures.
We describe the design and initial performance of the first 21 tesla Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The 21 tesla magnet is the highest field superconducting ...magnet ever used for FT-ICR and features high spatial homogeneity, high temporal stability, and negligible liquid helium consumption. The instrument includes a commercial dual linear quadrupole trap front end that features high sensitivity, precise control of trapped ion number, and collisional and electron transfer dissociation. A third linear quadrupole trap offers high ion capacity and ejection efficiency, and rf quadrupole ion injection optics deliver ions to a novel dynamically harmonized ICR cell. Mass resolving power of 150,000 (
m/Δm
50%
) is achieved for bovine serum albumin (66 kDa) for a 0.38 s detection period, and greater than 2,000,000 resolving power is achieved for a 12 s detection period. Externally calibrated broadband mass measurement accuracy is typically less than 150 ppb rms, with resolving power greater than 300,000 at
m/z
400 for a 0.76 s detection period. Combined analysis of electron transfer and collisional dissociation spectra results in 68% sequence coverage for carbonic anhydrase. The instrument is part of the NSF High-Field FT-ICR User Facility and is available free of charge to qualified users.
Graphical Abstract
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Detailed characterization of complex biological surfaces by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) requires instrumentation that is capable of high mass ...resolving power, mass accuracy, and dynamic range. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the highest mass spectral performance for MALDI MSI experiments, and often reveals molecular features that are unresolved on lower performance instrumentation. Higher magnetic field strength improves all performance characteristics of FT-ICR; mass resolving power improves linearly, while mass accuracy and dynamic range improve quadratically with magnetic field strength. Here, MALDI MSI at 21T is demonstrated for the first time: mass resolving power in excess of 1 600 000 (at m/z 400), root-mean-square mass measurement accuracy below 100 ppb, and dynamic range per pixel over 500:1 were obtained from the direct analysis of biological tissue sections. Molecular features with m/z differences as small as 1.79 mDa were resolved and identified with high mass accuracy. These features allow for the separation and identification of lipids to the underlying structures of tissues. The unique molecular detail, accuracy, sensitivity, and dynamic range combined in a 21T MALDI FT-ICR MSI experiment enable researchers to visualize molecular structures in complex tissues that have remained hidden until now. The instrument described allows for future innovative, such as high-end studies to unravel the complexity of biological, geological, and engineered organic material surfaces with an unsurpassed detail.
Successful high-throughput characterization of intact proteins from complex biological samples by mass spectrometry requires instrumentation capable of high mass resolving power, mass accuracy, ...sensitivity, and spectral acquisition rate. These limitations often necessitate the performance of hundreds of LC–MS/MS experiments to obtain reasonable coverage of the targeted proteome, which is still typically limited to molecular weights below 30 kDa. The National High Magnetic Field Laboratory (NHMFL) recently installed a 21 T FT-ICR mass spectrometer, which is part of the NHMFL FT-ICR User Facility and available to all qualified users. Here we demonstrate top-down LC-21 T FT-ICR MS/MS of intact proteins derived from human colorectal cancer cell lysate. We identified a combined total of 684 unique protein entries observed as 3238 unique proteoforms at a 1% false discovery rate, based on rapid, data-dependent acquisition of collision-induced and electron-transfer dissociation tandem mass spectra from just 40 LC–MS/MS experiments. Our identifications included 372 proteoforms with molecular weights over 30 kDa detected at isotopic resolution, which substantially extends the accessible mass range for high-throughput top-down LC–MS/MS.
Wildfires affect soils through the formation of pyrogenic organic matter (pyOM) (e.g., char and soot). While many studies examine the connection between pyOM persistence and carbon (C) composition, ...nitrogen (N) transformation in wildfire-impacted systems remains poorly understood. Thermal reactions in wildfires transform biomass into a highly complex, polyfunctional, and polydisperse organic mixture that challenges most mass analyzers. High-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is the only mass analyzer that achieves resolving powers sufficient to separate species that differ in mass by the mass of an electron across a wide molecular weight range (m/z 150–1500). We report enhanced speciation of organic N by positive-ion electrospray ionization (ESI) that leverages ultrahigh resolving power (m/Δm 50% = 1 800 000 at m/z 400) and mass accuracy (<10–100 ppb) achieved by FT-ICR MS at 21 T. Isobaric overlaps, roughly the mass of an electron (M e– = 548 μDa), are resolved across a wide molecular weight range and are more prevalent in positive ESI than negative ESI. The custom-built 21 T FT-ICR MS instrument identifies previously unresolved mass differences in C c H h N n O o S s formulas and assigns more than 30 000 peaks in a pyOM sample. This is the first molecular catalogue of pyOM by positive-ion ESI 21 T FT-ICR MS and presents a method to provide new insight into terrestrial cycling of organic carbon and nitrogen in wildfire impacted ecosystems.
Per- and polyfluoroalkyl substances (PFASs) are a large family of thousands of chemicals, many of which have been identified using nontargeted time-of-flight and Orbitrap mass spectrometry methods. ...Comprehensive characterization of complex PFAS mixtures is critical to assess their environmental transport, transformation, exposure, and uptake. Because 21 tesla (T) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the highest available mass resolving power and sub-ppm mass errors across a wide molecular weight range, we developed a nontargeted 21 T FT-ICR MS method to screen for PFASs in an aqueous film-forming foam (AFFF) using suspect screening, a targeted formula database (C, H, Cl, F, N, O, P, S; ≤865 Da), isotopologues, and Kendrick-analogous mass difference networks (KAMDNs). False-positive PFAS identifications in a natural organic matter (NOM) sample, which served as the negative control, suggested that a minimum length of 3 should be imposed when annotating CF2-homologous series with positive mass defects. We putatively identified 163 known PFASs during suspect screening, as well as 134 novel PFASs during nontargeted screening, including a suspected polyethoxylated perfluoroalkane sulfonamide series. This study shows that 21 T FT-ICR MS analysis can provide unique insights into complex PFAS composition and expand our understanding of PFAS chemistries in impacted matrices.
Fourier transform ion-cyclotron resonance mass spectrometry (FT-ICR MS) is the only mass analyzer that can resolve the molecular complexity of natural organic matter at the level of elemental ...composition assignment. Here, we leverage the high dynamic range, resolving power, resistance to peak coalescence, and maximum ion number and ion trapping duration in a custom built, 21 tesla hybrid linear ion trap /FT-ICR mass spectrometer for a dissolved organic matter standard (Suwanne River Fulvic Acid). We compare the effect of peak-picking threshold (3σ, 4σ, 5σ, and 6σ) on number of elemental composition assignments, mass measurement accuracy, and dynamic range for a 6.3 s transient across the mass range of m/z 200–1200 that comprises the highest achieved resolving power broadband FT-ICR mass spectrum collected to date. More than 36 000 species are assigned with signal magnitude greater than 3σ at root-mean-square mass error of 36 ppb, the most species identified reported to date for dissolved organic matter. We identify 18O and 17O isotopologues and resolve isobaric overlaps on the order of a few electrons across a wide mass range (up to m/z 1000) leveraging mass resolving powers (3 000 000 at m/z 200) only achievable by 21 T FT-ICR MS and increased by ∼30% through absorption mode data processing. Elemental compositions unique to the 3σ span a wide compositional range of aromaticity not detected at higher peak-picking thresholds. Furthermore, we leverage the high dynamic range at 21 T FT-ICR MS to provide a molecular catalogue of a widely utilized reference standard (SRFA) to the analytical community collected on the highest performing mass analyzer for complex mixture analysis to date. This instrument is available free of charge to scientists worldwide.
Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has exposed the ultracomplexity of fossil fuels, thereby validating the compositional trends that rule petroleum distillation, ...known as the Boduszynski Continuum. Routine FT-ICR MS analysis of a single crude oil sample can reveal tens-of-thousands of unique molecular formulas; however, currently available ionization methods suffer from limitations for such complex mixtures that are not yet completely understood. Simply put, MS detects ions, and thus, it depends heavily on the ability of ion sources to indiscriminately volatilize and subsequently ionize samples of interest. Despite advances in soft ionization methods, the characterization of complex matrices remains a challenge due to the lack of an ion source, commercial or custom-built, that can vaporize and ionize all compounds without bias, save analyte concentration. However, atmospheric pressure photoionization (APPI) has been shown to provide the most uniform ion production for mixtures of petroleum model compounds and real samples, with little to no fragmentation. In this work, we investigated the molecular composition of PetroPhase 2017 asphaltenes and its extrography fractions, with a focus on the total vanadium content and molecular composition of vanadyl porphyrins as a function of aggregate size distribution, accessed through separate experiments: online gel permeation chromatography (GPC) inductively coupled plasma–MS (ICP–MS) and online GPC APPI FT-ICR MS (at 21 T). The results reveal that the extrography separation provides asphaltene fractions (i.e., acetone, Hep/Tol, and Tol/THF/MeOH) enriched in 51V-containing compounds with distinctive aggregate size distributions. The acetone fraction features smaller aggregate sizes, as it elutes later in the GPC chromatogram than Hep/Tol and Tol/THF/MeOH fractions, and overall, presents up to ∼14-fold higher ionization efficiency in APPI. Such behavior suggests a correlation between aggregate size and production efficiency of monomeric ions in APPI. Bulk compositional trends accessed by GPC separation and highlighted by ICP–MS detection indicate that despite multiple separation steps (i.e. extrography followed by GPC), APPI FT-ICR MS can only access ∼37% of the total V-containing compounds. Although the more stable/larger aggregates dominate the size distributions of all asphaltene samples studied, it is the weakly aggregated/monomeric species that are preferentially observed by APPI-MS. Tendencies in the molecular composition of vanadyl porphyrins and S/O-containing compounds strongly suggest that London forces might be central in the self-assembly process of asphaltene nanoaggregates to produce more massive clusters. The results demonstrate that the observed compositional trends (albeit limited) can be accessed when coupling advanced chromatographic separations with online high-field FT-ICR MS detection.
It has been known for 35 years that phase correction of FTICR data can in principle produce an absorption-mode spectrum with mass resolving power as much as a factor of 2 higher than conventional ...magnitude-mode display, an improvement otherwise requiring a (much more expensive) increase in magnetic field strength. However, temporally dispersed excitation followed by time-delayed detection results in steep quadratic variation of signal phase with frequency. Here, we present a robust, rapid, automated method to enable accurate broadband phase correction for all peaks in the mass spectrum. Low-pass digital filtering effectively eliminates the accompanying baseline roll. Experimental FTICR absorption-mode mass spectra exhibit at least 40% higher resolving power (and thus an increased number of resolved peaks) as well as higher mass accuracy relative to magnitude mode spectra, for more complete and more reliable elemental composition assignments for mixtures as complex as petroleum.
We present a solid-phase extraction method followed by derivatization with a charged tag to characterize ketone/aldehyde-containing functionalities (proposed photo-oxidation transformation products) ...in weathered petroleum by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). A photo-oxidation-only microcosm mimics solar irradiation of crude oil in the environment after an oil spill. A biodegradation-only microcosm enables independent determination as to which of the two weathering processes contributes to the formation of oil-soluble ketone/aldehyde species. Results confirm that photo-oxidation produces ketones/aldehydes in crude oil when exposed to solar radiation in laboratory experiments, whereas biodegraded oil samples do not produce ketone/aldehyde compounds. Field samples collected after different time periods and locations after the Deepwater Horizon oil spill are also shown to contain ketones/aldehydes, and comparison of field and photo-oxidation-only microcosm transformation products reveal remarkable similarity. These results indicate that the photo-oxidation microcosm comprehensively represents ketone/aldehyde-formation products in the field, whereas the biodegradation microcosm does not. Solid-phase extraction coupled with derivatization leads to selective identification of ketone/aldehyde species by MS. Although improved dynamic range and slightly reduced mass spectral complexity is achieved by separation/derivatization, comprehensive molecular characterization still requires mass resolving power and mass accuracy provided by FT-ICR MS.
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